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Pound (mass)
The pound or pound-mass (abbreviations: lb, lb''m, '''lbm', ℔ |accessdate=28 April 2011}} ) is a of used in the imperial, United States customary and other . A number of different definitions have been used, the most common today being the international avoirdupois pound which is legally defined as exactly 0.45359237 s. The unit is descended from the (hence the abbreviation "lb"); the name pound is a adaptation of the Latin phrase libra pondo, 'a pound weight'. , s.v. 'pound' Usage of the unqualified term pound reflects the historical conflation of mass and weight resulting from the near uniformity of gravity on Earth. This accounts for the modern distinguishing terms pound-mass and . Current use The United States and countries of the agreed upon common definitions for the pound and the . Since 1 July 1959, the international avoirdupois pound has been defined as exactly 0.45359237 kg.National Bureau of Standards, Appendix 8; National Physical Laboratory, P H Bigg et al. : Re-determination of the values of the imperial standard pound and of its parliamentary copies in terms of the international kilogramme during the years 1960 and 1961; Sizes.com: pound avoirdupois. In the United Kingdom, the use of the international pound was implemented in the Weights and Measures Act 1963.Quoted by Laws LJ in kilogram exactly.|''Weights and Measures Act'', 1963, Section 1(1)}} An avoirdupois pound is equal to 16 avoirdupois s and to exactly 7,000 grains. The conversion factor between the kilogram and the international pound was therefore chosen to be divisible by 7, and an (international) grain is thus equal to exactly 64.79891 s. Historic use Historically, in different parts of the world, at different points in time, and for different applications, the pound (or its translation) has referred to broadly similar but not identical standards of mass or force.The pound is often described as a unit of "weight", and the word "weight" can refer to either mass or force depending on context. Historically and in common parlance, "weight" refers to mass, but as used in modern physics is a force. In Britain A number of different definitions of the pound have been used in Britain. Amongst these are the avoirdupois pound and the obsolete tower, merchant's, and London pounds.Grains and drams, ounces and pounds, stones and tons. Personal notes. The weight of precious metals when given in pounds and/or ounces usually assumes Troy pounds and ounces; these units are not otherwise used today. Historically the was a tower pound of silver. In 1528 the standard was changed to the Troy pound. In the United States In the United States, the avoirdupois pound as a unit of mass has been officially defined in terms of the kilogram since the Mendenhall Order of 1893. That Order defined the pound to be 2.20462 pounds to a kilogram. The following year this relationship was refined as 2.20462234 pounds to a kilogram, following a determination of the British pound. According to a 1959 publication, the international pound differed from the United States 1894 pound by approximately one part in 10 million. The difference is so insignificant that it can be ignored for almost all practical purposes. "In Great Britain, the Yard, the Avoirdupois Pound, the troy pound, and the Apothecaries pound are identical with the units of the same names used in the United States." (The introduction to this appendix makes it clear that the appendix is only for convenience and has no normative value: "In most of the other tables, only a limited number of decimal places are given, therefore making the tables better adopted to the average user.") Roman libra The libra (Latin for "scales / balance") is an of mass that was equivalent to approximately 328.9 grams. It was divided into 12 uncia, or ounces. The libra is the origin of the abbreviation for pound, lb. The commonly used abbreviation lbs to indicate the plural unit of measurement does not reflect Latin usage, in which lb is both the singular and plural abbreviation. Byzantine litra The Byzantine litra, more specifically the logarikē or chrysaphikē type used for gold, was equivalent to between 319 and 324 grams. French livre Since the Middle Ages, various pounds (livre) have been used in France. Since the 19th century, a livre has referred to the metric pound, 500g. The livre esterlin was equivalent to about 367.1 g and was used between the late 9th century and the mid-14th century. The livre poids de marc or livre de Paris was equivalent to about 489.5 grams (7,555 gr) and was used between the 1350s and the late 18th century. It was introduced by the government of . The livre métrique was set equal to the kilogram by the decree of 13 Brumaire an IX between 1800 and 1812. This was a form of official metric pound. The livre was defined as 500 grams, by the decree of 28 March 1812. It was abolished as a unit of mass effective 1 January 1840 by a decree of 4 July 1837, but is still used informally. German and Austrian Pfund Originally derived from the Roman libra, the definition varied throughout Germany in the Middle Ages and onward. The measures and weights of the were reformed in 1761 by Empress . The unusually heavy Habsburg (civil) pound of 16 ounces was later defined in terms of 560.012 grams. reforms in 1809 and 1811 adopted essentially the same standard pound. In , a reform in 1816 defined a uniform civil pound in terms of the Prussian foot and distilled water, resulting in a Prussian pound of 467.711 grams. Between 1803 and 1815 all German regions west of the were French, organised in the s: , , , and . As a result of the Congress of Vienna these became part of various German states. However, many of these regions retained the metric system and adopted a metric pound of precisely 500 grams. In 1854 the pound of 500 grams also became the official mass standard of the , but local pounds continued to co-exist with the Zollverein pound for some time in some German states. Nowadays, the term Pfund is still in common use and universally refers to a pound of 500 grams. Russian funt The Russian pound (Фунт, funt) is an of mass. It is equal to 409.51718 grams. Skålpund The Skålpund was a Scandinavian measurement that varied in weight between regions. From the 17th century onward, it was equal to 425.076 grams in Sweden but was abandoned in 1889 when Sweden switched to the metric system. In Norway the same name was used for a weight of 498.1 grams. In Denmark it equalled 471 grams. In the 19th century Denmark followed Germany's lead and redefined the pound as 500 grams. Jersey pound A Jersey pound is an obsolete unit of mass used on the island of from the 14th century to the 19th century. It was equivalent to about 7,561 grains (490 grams). It may have been derived from the . Trone pound The trone pound is one of a number of . It was equivalent to between 21 and 28 avoirdupois ounces (about 600-800 grams). Metric pounds In many countries upon the introduction of a , the pound (or its translation) became an informal term for 500 grams, The Dutch pond is an exception. It was officially redefined as 1 kilogram, with an ounce of 100 grams, but people seldom use it this way. In daily life pond is exclusively used for amounts of 500 grams, and to a lesser extent, ons for 100 grams. In the term is Pfund, in , in Dutch pond, in and libra, in libbra, and in and pund. Though not from the same linguistic origin, the Chinese jin (also known a " ") has a modern definition of exactly 500 grams, divided into ten cun. Traditionally about 605 grams, the jin has been in use for more than two thousand years, serving the same purpose as "pound" for the common-use measure of weight. Hundreds of older pounds were replaced in this way. Examples of the older pounds are one of around 459 to 460 grams in Spain, Portugal, and Latin America; one of 498.1 grams in Norway; and several different ones in what is now Germany. Although the use of the pound as an informal term persists in these countries to a varying degree, scales and measuring devices are denominated only in grams and kilograms. A pound of product must be determined by weighing the product in grams as the use of the pound is not for trade within the . Use in weaponry Smoothbore cannon and carronades are designated by the weight in imperial pounds of round solid iron shot of diameter to fit the barrel. A cannon that fires a six-pound ball, for example, is called a six-pounder. Standard sizes are 6, 12, 18, 24, 32 and 42 pounds; 68-pounders also exist, and other nonstandard weapons use the same scheme. See . A similar definition, using balls, exists for determining the of s. Notes External links Conversion between units * Yahoo Conversion Calculator. * U.S. National Institute of Standards and Technology Special Publication 811 * National Institute of Standards and Technology Handbook 130 Category:Customary units in the United States Category:Imperial units Category:Units of mass Category:Metricated units